Hybrid vehicles and electric vehicles are gaining popularity due to their lowered operating costs and environmental benefits, among other reasons. The lowered operating costs may be attributable both to efficiency improvements in vehicle operation and the capability to rely on an energy source that is comparatively lower in cost than fuel (such as in the case of plug-in electric vehicles, for example). In particular, for vehicles with electric motor drive systems, one of the most significant efficiency improvements is the ability to perform regenerative braking, which converts a vehicle's kinetic energy to electrical energy during vehicle deceleration, and then stores the energy. Another significant efficiency improvement is the ability to shut down parts of the vehicle's power system when the vehicle is stopped, thereby eliminating engine idling, which is typical of vehicles equipped with internal combustion engines.
In hybrid vehicles, starting and stopping of the engine and regenerative braking are typically triggered by the driver depressing the brake pedal. To provide appropriate inputs to a system computer, such vehicles typically employ a simple switch as a position sensor on a brake pedal. The system computer cannot gauge a degree of pedal motion and is limited to determining whether there is an indication that the pedal is depressed. The brake pedal switch is typically used for non-critical control functions and used to control illumination of rear brake lights of the vehicle. The typical switch configuration presents a single-point-of-failure mode for hybrid or electric vehicles in terms of energy-savings functionality. Further, diagnosing failures of discrete inputs such as brake switches is difficult due to the limitations of out-of-range, open-circuit and short-circuit detection techniques.